Caian鈥檚 role in re-writing the genetic code
- 02 September 2025
- 2 minutes
The same genetic code is universal across all known life. Now scientists including Cicely Day (Biological Sciences MPhil 2023) have built a bacterium that runs on a different, simplified genetic code.
Cicely collaborated with colleagues during her Master鈥檚 in programme leader Professor Jason Chin鈥檚 laboratory on a paper, which has been published in the academic journal .
The natural genetic code uses 64 different triplets of DNA bases, known as codons, to encode the 20 standard amino acids and stop signals. When the amino acids are assembled, they form proteins. However, the genetic code is redundant, with several codons encoding the same amino acid or stop signal.
Having previously synthesised an entire E. coli genome which runs on a 61-codon genetic code, named Syn61, Professor Chin鈥檚 group has gone a step further, synthesising Syn57, an E. coli strain which runs on only 57 codons. There are 101,000 changes to its DNA, making it the most recoded synthetic genome to date.
Cicely joined the project when the fragments of synthetic DNA used to build Syn57 had been assembled and the team were using these fragments to replace the natural genome with the recoded genome.
鈥淲hat we were observing was that the more we were making this E. coli genome run on a non-natural genetic code, the less and less fit it was becoming.鈥 Cicely says. 鈥淚鈥檓 a biologist by training, so this was quite an exciting time for me.
鈥淭hen it was the idea of how we could evolve it to become fitter. That鈥檚 what my thesis was looking at: how can we characterise this unnatural organism and then use this information to evolve the genome, to make it grow faster and actually be viable.鈥
By freeing up redundant codons, scientists can reassign them to unnatural amino acids, which could allow the manufacture of novel drugs, for example.
Cicely believes the completion and publication of the project, which will be prominent on her CV as she pursues an academic career, was made sweeter by working with and sharing the success as a team.
鈥淚t was a complete privilege to be involved,鈥 she adds.
Cicely has remained at the Medical Research Council鈥檚 Laboratory of Molecular Biology as a Research Assistant, and is in the process of applying for a PhD.
Professor Chin is now founding director of the at the University of Oxford.
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